Matrices, Fish/Cooked Seafood, Meat/Frozen Cooked Meat Products, Nuts and Nut Products/Tree Nut Meats. Approved By, AOAC. Method Number, recommended by AOAC Official Method (1). The ap- propriate dilutions were analyzed by the AOAC pour plate method (AOAC ) and the SimPlate . AOAC Compendium of Methods for the Microbiological Examination of Foods 4th Edition: Chapter 7. FDA Bacteriological Analytical Manual: Chapter 3.
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References 1 Roth, J. However, there was a significant difference aoad the VRB Redigel and all the other methods with the Duncan mean comparison for coliforms. The Redigel Pectin Gel Method consists of two parts, the first being the liquid portion containing the ingredients plus the gelling agent, and the second part consisting of a petri dish coated with a thin gel layer containing calcium ions.
Red or pink colonies were counted and recorded as total coliforms. The mean comparisons for each method and level indicated no significant differences among any of the methods except for Petrifilm EC with ColiChrome 2 Redigel and VRB Redigel at the low levels for coliforms. The MPN and ColiChrome 2 Redigel differed significantly in two other instances, those being in the corn at the low level and the pasteurized milk at the high level of bacteria.
966.32 ColiChrome 2 Redigel method consists of a medium incorporating growth nutrients, selective factors and two substrates containing chromogenic indicators, one aoaf detect activity and one to detect glucuronidase activity. The ColiChrome 2 Redigel plates were incubated for 48 h at 35 C.
The food groups tested were as follows: It is not only bulky and time consuming to set up, but confirmed results may not be available for days.
However, comparison of ColiChrome 2 Redigel with the other 2 rapid methods showed Therefore, total coliform colonies appear as red colonies in the clear medium. Dairy – Seafoods – Meats – Vegetables cheddar cheese fish frozen beef raw ground broccoli frozen cottage cheese oysters fresh meat pot pie frozen corn frozen milk pasteurized shrimp fresh turkey raw ground mushrooms fresh milk raw yogurt.
The mean comparisons for each method and level indicated no significant differences among any of the methods aoqc levels. Spices – Grain Products – Nutmeat pepper black ground flour peanuts raw thyme rice walnuts. Since both of these methods are also AOAC approved, we felt aosc such additional comparisons would be most informative and helpful.
Due to our awareness that MPN methods have been reported to exhibit significant variability 7the authors 966.223 to also include as part of the study a comparison to the VRB Redigel method for total coliforms and a comparison to the Petrifilm EC method for total coliforms and E. The decision to base this study on a comparison of ColiChrome 2 Redigel to the standard MPN method was influenced by the fact that 966.32 recent collaborative studies have been done and approved on the basis of this format 5,6.
696.23 is particularly interesting to compare the three methods with the MPN method.
Percentage of samples falling within MPN confidence intervals for each method were as follows: The mean comparisons for each method and level indicated a significant difference between the MPN and all other methods at the low levels for coliforms, with no significant difference at high and medium levels.
This oyster tissue activity apparently interferes with the obvious expression of red coliform CFUs. Following the introduction of the technology by RCR Scientific, the idea was copied by most of the major media makers worldwide since the RCR patent only covered the U.
Also, none of the mean comparisons for each method and level differed significantly. The precollaborative study therefore has lain dormant since then until the reacquisition of the ColiChrome technology by RCR Scientific who sold it to Micrology Laboratories Brief comments on each of the food products follows.
Red colonies were recorded as total coliforms and purple colonies were recorded as E. VRB Redigel plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h.
This study was designed in consultation with Dr. At 24 h, two typical isolated colonies were picked from each EMB plate and transferred to individual plate count agar slants.
The mean comparisons for each method and level indicated no significant differences among the MPN and any of the other methods except for MPN and Petrifilm EC at the medium level for coliforms. Redigel is an agar plate substitute whose only basic difference to standard agar plate media is the substitution of a low methoxyl pectin for agar as the gelling agent in the media.
The data presented in this paper were from the 24 h. When the liquid portion is poured into the pretreated petri dish, the calcium ions diffuse upward through the medium and complex with the pectin to form an agar-like calcium pectate gel.
Following are some observations and comments for Duncan’s Multiple Range Test for coliforms. The mean comparisons for coliforms with each method and level indicated no significant differences between the MPN and all other methods. Total coliforms produce the enzyme galactosidase which cleaves the first substrate to form an insoluble red dye. Both red and purple blue colonies were counted at both 24 h and 48 h.
The entire medium may take on a very light-pink cast, seeming to indicate a high galactosidase level in the medium from the oyster tissue. Red and blue gassing colonies were counted at 24 h and the sum of the two was recorded as total coliforms.
The study was submitted to the AOAC for the purpose of receiving permission to do an official collaborative study with the goal of having ColiChrome 2 Redigel being approved as an official method of the AOAC.
Precollab Study – Micrology Labs
This kind of result raises the question 966.2 the accuracy of the MPN method for those cases. Petrifilm plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h. The procedures were followed according to instructions provided with the product and the counts were made in accordance with the protocol established in the collaborative study of the product 6.